Metering method and device

ABSTRACT

A method and apparatus for metering highly viscous, paste-like material, in particular printing ink, e.g. offset printing ink, from a metering valve. The metering valve in dependence upon the determined quantity of material delivered into a container is closed and then the residual material left suspended at the outlet side of the metering valve is removed by a roller.

BACKGROUND OF THE INVENTION

The invention relates to a method of metering highly viscous, paste-likematerial, in particular printing ink, e.g. offset printing ink, from ametering valve, wherein the metering valve in dependence upon thedetermined quantity of material delivered into a container or the likeis closed and then the residual material left suspended at the outletside of the metering valve is removed, as well as to a metering devicefor metering highly viscous, paste-like material.

Metering highly viscous, paste-like material which, for example, has aviscosity in excess of 2000 pascal/sec is difficult in practice, asbecomes particularly clear, for example, when attempting to meterdifferent offset printing inks into a container in such a way that themixed product obtained is of a precisely defined shade of colour.

It is known to supply highly viscous, paste-like materials in the formof offset printing inks from drum-shaped containers under high pressureeach to a metering valve, from which a stream or strand of the materialis then discharged into a container coupled to a weighing device, sothat the metering process, generally controlled by a computer, isterminated when the preselected quantity of material has been dischargedfrom the metering valve. The offset printing inks of other colour shadesare correspondingly discharged via further metering valves into thecontainer to thereby obtain the desired mixture of material of apreselected colour shade.

While good control of the metering valve may be achieved despite thehigh viscosity of the paste-like material being discharged, so that thedesired quantity of material is metered with sufficient accuracy intothe container or the like, a considerable problem is presented by thefact that, after closure of the metering valve, a certain amount ofresidual material is left suspended from its underside, the quantitydepending on the composition of the material, the ambient temperature orthe like, i.e. not being precisely defined. Apart from the fact that thedischarge of said residual material into the container containing themetered material leads to an inaccuracy which may considerably alter themixing ratio, it is also extremely difficult to remove said residualmaterial from the underside of the valve.

In practice, removal of the residual material is frequently effectedwith the aid of a spatula, to which, however, the residual material thenadheres and has to be scraped off by hand at a receiving container. Theresidual material is therefore generally left clinging to the edge ofthe receiving container and contaminates said container, making it nolonger easy to close with a lid.

An attempt has already been made to remove the residual material byproviding air nozzles in the region of the underside of the meteringvalve in order to use the air jets exiting from such nozzles to detachthe residual material suspended from the underside of the meteringvalve. Apart from the fact that this would, at best, lead to thesubstantially unknown quantity of residual material additionally fallinginto the container already containing the desired quantity of materialand hence invalidating the metering, in many cases owing to theirregular action of the air jets an approximately lateral spinning-awayof the residual material was effected so that the residual material felloutside of the region of the container onto the floor or even soiled theclothing of the operator. Stains caused by printing ink in particularare extremely stubborn and are removable, if at all, only with greatdifficulty.

SUMMARY OF THE INVENTION

The object of the invention is to provide a simple and effective way ofremoving the residual material which, when metering highly viscous,paste-like materials, is left suspended from the metering valve afterclosure.

To achieve said object, according to the invention a method of the typedescribed initially is improved in such a way that, for removal of theresidual material, a roller disposed just below and to one side of themetering valve is brought into contact with the residual material, theroller rotating about its substantially horizontal longitudinal axis insuch a way that the peripheral region of the roller coming into contactwith the residual material moves in an upward direction.

With said method, removal of the residual material suspended from theunderside of the metering valve is therefore effected in that,immediately after closure of the metering valve, the surface of arotating roller is brought, as close to the underside of the meteringvalve as possible but without touching it, into contact with theresidual material which then adheres to the roller surface and as aresult of the upward movement of the contact region of the rollersurface is conveyed in an upward direction. Thereby a type of winding-onmovement of the residual material occurs, until even the bottom end ofthe suspended residual material is gripped and carried away by theroller, as well as a lateral detachment from the underside of themetering valve.

Tests have shown that residual material in the form of offset printingink adheres extremely well to, and may be transported away by the smoothsurface of a steel roller. Both the structure and the material of theroller surface, as well as the roller diameter and the rotational speeddepend, however, on the residual material in question and its actualstate and may be optimally selected by trials.

To prevent the build-up on the roller surface of a thick layer ofresidual material which, on the one hand, could impede the continuedtake-up of residual material and, on the other hand, may come intomaterial-stripping contact with the underside of the metering valve, theresidual material taken up by the roller may preferably be removed fromthe roller surface at the opposite side to the take-up side by means ofa doctor blade so that it is always a substantially cleaned surfaceregion of the roller moving towards the residual material.

The invention further relates to a metering device for metering highlyviscous, paste-like material, in particular printing inks, e.g. offsetprinting inks, comprising at least one metering valve, which isconnectable to a material store and to which the material is supplied athigh pressure, comprising a weighing device for determining the quantityof material discharged from the metering valve, comprising a controldevice for influencing the opening state of the metering valve as afunction of the discharged quantity of material and comprising a devicefor removing the residual material which is left suspended from themetering valve after closure.

A metering device of said type, whose construction could correspondsubstantially to that of the device of EP 0 516 897 A1, is according tothe invention improved in such a way that the device for removal ofresidual material comprises a roller, which may be driven rotatablyabout its longitudinal axis and is movable relative to the meteringvalve between a position of rest at a distance from the material exitingfrom the metering valve and an operating position in which the roller,with its longitudinal axis aligned substantially horizontally, issituated just below the metering valve and in contact with the residualmaterial so that, as the roller rotates, the contact between residualmaterial and roller surface occurs, which effects adhesion of theresidual material to the upward-moving region of the roller surface.

By means of the metering device according to the invention, the residualmaterial suspended from the metering valve after closure of said valvemay be removed in the manner described above with reference to themetering method.

The roller may be held on a laterally displaceable carriage. Saidcarriage preferably has the shape of a trough, the roller projectingbeyond the side wall of said trough nearer the metering valve. A doctorblade may be provided in the trough, said doctor blade for strippingaway residual material being in engagement with the peripheral wall ofthe roller lying opposite the projecting part of the roller so that thedetached residual material is received by the trough.

The trough may have a trough chamber, which is separate from the doctorblade and into which dips a rotatably drivable cleaning brush, whoseaxis of rotation is disposed parallel to the longitudinal axis of theroller and whose bristles upon displacement of the carriage beyond theoperating position come into engagement with the underside of themetering valve having the outlet opening. The rotating cleaning brush ismoistened with a solvent for the residual material to enable theresidual material to be, on the one hand, easily separated from themetering valve and, on the other hand, flushed out of the cleaningbrush.

A motor forming the rotary drive for the roller and the cleaning brushis preferably disposed on the carriage. The rotational speed of themotor is advantageously continuously variable to enable the rotationalspeed of the roller to be adapted to the properties of the material.

Since an easily ignitable solvent may be situated in the region of thecarriage and since often the material too is highly inflammable, apneumatic motor is advantageously used as a motor, said motor moreoverenabling speed control in a simple manner by means of throttles or thelike.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail below with reference to thedrawings which illustrate an embodiment.

FIG. 1 is a diagrammatic partial view of a metering valve, below whichare disposed a container and a carriage bearing the roller and acleaning brush.

FIG. 2 is a plan view of the carriage according to FIG. 1.

FIG. 3 is an extremely diagrammatic sectional view of the bottom part ofthe metering valve of FIG. 1 in its fully open state for dischargingmaterial.

FIG. 4 is a view corresponding to FIG. 3 of the metering valve in anopen position which reduces the discharge of material.

FIG. 5 is a view corresponding to FIGS. 3 and 4 of the metering valve,closed after the discharge of material and having residual materialsuspended therefrom, and of the roller of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The arrangement diagrammatically shown in FIG. 1 comprises a meteringvalve 1, whose housing 3 is fastened on a carriage plate 2 and whoseoperating device 10 is coupled to an operating part 4 of the meteringvalve 1 in the manner described, for example, in EP 0 516 897 A1. Thematerial to be metered is supplied through a lateral inlet 6 to themetering valve 1 and, when the metering valve 1 is opened, exits at theunderside of the housing 3 and is poured into a container 11 standing ona balance 12 and situated below the metering valve 1, which has beensuitably positioned through displacement of the carriage plate 2. In thecustomary manner for such metering devices, the balance 12 is coupled toa computer, preferably a personal computer (indicated by SPS/PC) which,in accordance with the actual weight determined by the balance, controlsthe operating device 10 for the metering valve 1 as a function of theknown properties of the material being discharged in such a way that thedesired quantity of material 11 is discharged and the metering valve 1subsequently closed.

To enable highly viscous, paste-like material having a viscosity inexcess of 2000 pascal/sec, such as for example printing inks, inparticular offset printing inks, to be discharged by such anarrangement, the material is delivered, e.g. by a known barrel-emptyingdevice which feeds material out of a barrel by pushing a pressure platedown onto the barrel contents with a pressure in the order of magnitudeof 100 bar, through a pipe to the inlet 6 of the metering valve 1 whereit enters at a pressure of more than 50 bar. Given the presence ofmaterial in the metering valve 1, when the metering valve 1 is opened bythe closing element 5 of the metering valve 1 being raised throughactivation of the operating device 10 (FIG. 3), the highly viscous,paste-like material 50 exits through the valve opening 7 thus formed inthe valve housing 3 in the form of a material stream or strand 51 whichhas an outside diameter substantially corresponding to the minimumdiameter of the valve opening 7. Once said material stream or strand 51has filled the container 11 to the extent that the balance 12 determinesa value approaching the desired end value, the operating device 10effects a gradual closing of the closing element 5, with the result thatthe clear cross-section of the valve opening 7 is reduced in the mannerindicated in FIG. 4. The material stream or strand 52 then has adiameter of a considerably reduced dimension, i.e. a smaller quantity ofmaterial per unit of time is discharged into the container 11.

Upon closer approximation to the desired filling level of the container11, the closing element 5 is closed to a greater extent and, shortlybefore the desired filling quantity is reached, a reciprocating movementof the closing element 5 is effected so that said element progressivelyapproaches the closed position and, while so doing, also pumps smallquantities of material 50 out of the valve opening 7 until the balance12 determines metering of precisely the desired quantity of materialinto the container 11, whereupon the closing element 5 is held by theoperating device 10 in the closed position according to FIG. 5.

However, since the material 50 being discharged is highly viscous andpaste-like, residual material 53 still adheres to the underside of themetering valve 1 in the manner indicated in FIG. 5, said residualmaterial being suspended in a sharply tapering, elongated form from theunderside of the metering valve 1 and generally being rotationallysymmetrical relative to the centre line 7' of the valve opening 7.

As FIG. 1 shows, a carriage 15 supported on two guide rails 13, 14 anddriven by a pneumatic working cylinder 18 is provided below the meteringvalve 1 and is moved back and forth between the two positions indicatedin FIG. 1. The carriage 15 is substantially in the shape of a troughhaving a trough region 17, which is usually filled with a solvent or iswashed through by a solvent and in which a cylindrical cleaning brush 22is rotatably disposed, whose bristles, on the one hand, lie at adistance above the bottom of the trough region 17 and dip into thesolvent and whose bristles, on the other hand, project beyond the topedge of the trough region 17. Moreover, disposed in a further troughregion 16 is a roller 20, e.g. a steel roller with a smooth cylindricalsurface, which, at the side of the carriage 15 remote from the cleaningbrush 22, projects to a slight extent laterally beyond the trough region16. The roller 20 is supported with its longitudinal axis parallel tothe longitudinal axis of the cleaning brush 22 and projects beyond thetop edge of the trough region 16 and the trough region 17, although withthe maximum generating line it is located in a horizontal plane slightlybelow the top generating line of the cylindrical arrangement of bristletips of the brush 22. Thus, when the carriage 16 is displaced in themanner yet to be described between the two positions shown in FIG. 1,the roller 20 moves past the underside 8 of the metering valve 1 at aslight distance of about 1 to 2 mm below it, while the bristles of thebrush 22 come into cleaning engagement with said underside 8.

A doctor blade 21 is fastened in the trough region 16 at the oppositeside to the laterally projecting wall region of the roller 20 and isarranged in such a way that, when the roller 20 rotates in a clockwisedirection (FIGS. 1 and 5), the doctor blade scrapes highly viscous,paste-like material adhering to the roller surface off said surface sothat such material is retained in the chamber region 16.

During operation, the roller 20 and the brush 22 are driven via chains24, 25 by the pneumatic motor 23 so that they rotate in a clockwisedirection (FIG. 1), the rotational speed being continuously variable insuch a way that the roller 20 is rotated at a suitable speed for thematerial to be metered, while the speed of the brush 22 is uncriticalsince the brush merely effects a cleaning process to be described below.In one application case, the roller 20 had a diameter of around 30 mmand was driven at a speed of 60 rpm.

When, as described above, material 50 is metered into the container 11and at the end of the metering process, once the closing element 50 ofthe metering valve 1 has been closed, residual material 53 is suspendedfrom the metering valve, the carriage 15 is moved out of the positionaccording to FIG. 1, the position of rest of the roller 20, towards thecentre line 7' of the valve opening 7 into a position, the operatingposition of the roller 20, in which the peripheral region of therotating roller 20 projecting laterally beyond the trough region 16comes into contact with the residual material 53, so that the roller 20is situated in the position indicated in FIG. 5 or is moved into andthen beyond said position. As a result of the upward movement of theperipheral region of the rotatingly driven roller 20 in contact with theresidual material 53 and adhesion of such material to the rollersurface, the residual material 53 is carried along by the roller surfacein the direction of rotation and a kind of winding-on process for theresidual material 53 occurs, whereby such material is drawn continuouslyup towards the roller 20 and is taken up by the roller 20 until theresidual material 53 has been almost fully removed from the underside ofthe metering valve 1. During said "winding-on process", the residualmaterial 53 which has been taken up by the roller 20 is simultaneouslyremoved from the roller surface by the doctor blade 21 in the chamberregion 16 so that the roller region coming once more into contact withthe suspended residual material 53 is substantially free of material.

After said "winding-on process" by the roller 20, normally a very smallquantity of residual material is left adhering to the metering valve 1,said quantity being all the smaller, the narrower the gap between the"winding-on" roller 20 and the underside 8 of the metering valve 1.However, such gap has to be large enough reliably to prevent residualmaterial, which has been "wound" onto the roller 20, from sticking orbeing scraped off at the underside 8 of the metering valve 1.

Once the "winding-on process" is complete, the carriage 16 is displacedbeyond the operating position of the roller 20 so that the rotatablydriven cleaning brush 22 removes the residual material 53 still clingingto the underside of the metering valve 1, such process presenting noproblems owing to the small quantity of residual material because thismaterial is easily removed from the bristles of the brush 22 by thesolvent provided in the trough region 17.

The carriage 15 is finally moved out of the left position indicated inFIG. 1 back into the illustrated right position so that it is in aposition in which it may be moved back into the operating position ofthe roller 20 for the take-up of residual material.

We claim:
 1. A method of cleaning a metering valve having an outletside, so as to remove material suspended at the outlet side of themetering valve, comprising:providing a roller for cleaning; disposingthe roller just below and to one side of the metering valve; mountingthe roller for rotation about a substantially horizontal longitudinalaxis; and rotating the roller so as to bring a peripheral region of theroller undergoing a component of motion in a generally upward directioninto contact with the suspended material.
 2. The method according toclaim 1 further comprising the steps of:providing a doctor blade; andpositioning the doctor blade adjacent the roller surface at a pointremote from the point on the peripheral region of a roller whichcontacts the residual material in an upward direction, so as to removeat least a portion of the residual material carried by the roller.
 3. Ametering device for metering highly viscous, paste-like materialincluding:at least one metering valve having means for connection to asource of the material; weighing means for determining the quantity ofmaterial discharged from the metering valve; control means, responsiveto the weighing means to control opening of the metering valve; andmeans for removing material which is left suspended from the meteringvalve after valve closure; the improvement wherein the removal meanscomprises: a roller having a surface and a longitudinal axis; means formounting the roller for rotation about the longitudinal axis; means formoving the roller to the metering valve, between a rest position spacedfrom the path of material dispensed from the metering valve and anoperating position in which the roller is located below the meteringvalve in contact with the residual material such that, with rotation ofthe roller, a first portion of the roller surface has a component ofmovement which is generally upwardly moving, the roller located in theoperating position such that material suspended from the metering valveis contacted by the first portion of the roller surface and carried bythe roller surface.
 4. The metering device of claim 3 further comprisinga carriage carrying the roller; and means for laterally displacing thecarriage so as to move the roller between the rest position and theoperating position.
 5. The metering device of claim 4 wherein thecarriage comprises a trough having first and second opposed side walls,with the first side wall located nearer the metering valve than thesecond side wall;a doctor blade located adjacent the second side wall soas to strip away material carried on the roller surface; and the rollerpositioned with respect to the first side wall such that a portion ofthe roller surface extends outside of the trough.
 6. The metering deviceaccording to claim 5 wherein:the trough defines a trough chamber holdinga solvent for the suspended material; a cleaning brush having a rotationaxis; means for mounting the cleaning brush for rotation about therotation axis, with the rotation axis being generally parallel to thelongitudinal axis of the roller; and the cleaning brush containingbristles which contact the solvent in the trough chamber and which carrythe solvent to the underside of the metering valve.
 7. The meteringdevice according to claim 6 further comprising a motor carried on thecarriage and coupled to the roller and the cleaning brush for rotationaldriving of the roller and the cleaning brush.
 8. The metering deviceaccording to claim 7 wherein the motor has a continuously variableoutput speed.
 9. The metering device according to claim 8 wherein themotor is a pneumatic motor.
 10. The metering device of claim 3 whereinthe roller has an outer cylindrical surface.
 11. The metering deviceaccording to claim 10 wherein the roller includes a metallic cylinderwhich includes the outer surface.